The clutch-release bearing unit of this invention is installed in the clutch mechanism of a manual transmission or gear changer for an automobile, and is used for pushing the center of a diaphragm spring when changing gears with a push-type clutch, and is used for pulling the center of a diaphragm spring when changing gears with a pull-type clutch.
The clutch mechanism of the manual transmission or gear-changer comprises a flywheel that rotates together with the engine""s crankshaft, a clutch disk that faces the flywheel, a pressure plate that pushes the clutch disk toward the flywheel, a diaphragm spring that pushes the pressure plate toward the clutch disk, and a clutch-release bearing unit that moves freely along a guide shaft (front cover) that is located around the power-transmission shaft and changes the angle of inclination of the diaphragm spring as it moves in order to control the disengagement and engagement between the flywheel and the clutch disk.
Conventionally, for this kind of clutch mechanism there is the so-called push type that pushes the center of a diaphragm spring when disengaging the clutch (when separating the flywheel and clutch disk so that the rotating force of the crank shaft is not transmitted to the transmission by way of the aforementioned shaft), and a so-called pull type that pulls the center of the diaphragm spring when disengaging the clutch.
In either case of clutch mechanism, when disengaging the clutch, the aforementioned clutch-release bearing unit is displaced along the axial direction by the release fork which rocks when the clutch pedal is stepped on. In addition, by attaching one of the races of the release bearing of this clutch-release bearing unit to the center of the diaphragm spring directly or by way of some other member, it pushes or pulls the center of the diaphragm spring. In this condition, the aforementioned release bearing unit prevents the parts from rubbing against each other due to the relative rotation of the aforementioned race and the other race regardless of the rotation of the diaphragm spring.
FIGS. 1 and 2 show an example of a clutch-release bearing unit as disclosed in Japanese Patent Publication Toku Kai Hei 9-177827 to be installed in this kind of clutch mechanism. This clutch-release bearing unit 1 is installed in a push-type clutch mechanism and comprises a non-rotating sleeve 2 that slidingly moves freely along a cylindrical-shaped, non-rotating guide shaft 21 (front cover) that is installed in this clutch mechanism. The sleeve 2 is totally made of a synthetic resin, easily slidable, and formed in a cylindrical shape.
In addition, there is a ring-shaped flange 3 that is formed around the outer peripheral surface of the sleeve 2. In the example shown in the figure, this flange 3 is made out of the same synthetic resin as the sleeve 2, and is integrated in one piece with the sleeve 2. This flange 3 may also be made of metal, as disclosed in Japanese Patent Utility Model Publication Jitsu Kai Hei 6-73468, and the inner peripheral edge may be inserted in the sleeve 2 when forming the sleeve 2.
A release bearing 4 is supported by the surface on one side (left side in FIG. 1) of the flange 3. This release bearing 4 comprises an outer race 6 with an outer-race track 5 formed around its inner peripheral surface, an inner race 8 with an inner-race track 7 formed around its outer peripheral surface, and a plurality of rolling bodies (balls) 9 rotatably located between the outer-race track 5 and the inner-race track 7. In the example shown in the figure, the outer-race track 5 has a deep groove type, and the inner-race track 7 has an angular type. This release bearing 4 supports a radial load, as well as a thrust load in the direction of one side of the flange 3 (toward the right side in FIG. 1). This kind of release bearing 4 is supported on the surface on the one side of the flange 3 by retaining springs 10, that are fastened at two locations on the flange 3 opposite from each other in the radial direction (top and bottom in FIG. 2), such that it can displace a little in the radial direction (such that it can automatically center itself with respect to the diaphragm spring).
In the example in the figure, of the outer race 6 and the inner race 8 of the release bearing 4, the inner race 8 is formed by pressing a steel plate. By performing this kind of plastic processing based on pressing a steel plate, the inner-race track 7 is formed around the outer peripheral surface of the middle section of this inner race 8, a radially inward facing edge 11 is formed around its base end (right end in FIG. 1), and a curved section 12 is formed on the opposite end (left end in FIG. 1) by bending it outward in the radial direction in order to come into contact with the center of the diaphragm spring (not shown) for pressing.
Moreover, a metal slide plate 13, called an anvil, is attached to the surface on the other side of the flange 3 (right surface in FIG. 1), and it prevents friction with the flange 3, regardless of the sliding motion with the tip of the release fork (not shown).
Also, at two locations opposite each other in the radial direction on the outer peripheral edge of the surface on the other side of this flange 3, guide walls 14 for guiding the ends of the release fork are formed such that they are parallel with each other. Part of the retaining springs 10 pass through a hole 16 formed in both of these guide walls 14. Moreover, reinforcement ribs 15 are formed at a plurality of locations between the surface on the other side of the flange 3 and the outer peripheral surface of the sleeve 2, for maintaining strength against the thrust load that is applied to the flange 3 from the release bearing 4. Furthermore, the outer peripheral edge of seal rings 17a, 17b are fastened around the inner peripheral surface on both ends in the axial direction of the outer race 6 to seal both of the openings of the space where the rolling bodies 9 are located.
In the clutch-release bearing unit described above, it is desired that the synthetic resin sleeve 2, located such that it slides freely with respect to the guide shaft 21, has good capability of sliding with respect to the guide shaft 21, and that the sliding section has sufficient resistance to wear due to sliding between the sleeve 2 and the guide shaft 21 (especially in the case of an aluminum alloy). In addition to this, it is desired that these characteristics can be maintained over a long period of time.
However, in the case of the synthetic resin sleeve 2 used up until now, it was difficult to sufficiently satisfy these requests. In other words, up until plastic reinforced with glass fiber, such as polyamide 66 mixed with glass fiber, was used as the synthetic resin material for the sleeve 2, however in the case of this kind of glass-reinforced plastic sleeve 2, it was possible to maintain sufficient strength. On the other hand, it was difficult to maintain the desired ability to slide and the desired resistance to abrasion wear over a long period of time.
An objective of this invention is to provide a clutch-release bearing unit with the above problems in mind.
Another objective of this invention is to provide a clutch-release bearing unit wherein it is possible to improve the sliding capability of the sleeve with respect to the guide shaft as well as its resistance to abrasion wear over a long period of time.